We have 3 Mailbox store servers. I noticed when I create a user, it has an option set by default to automatically choose which server to put each users mailbox. Does anyone know how it chooses the server to put the users on? I know I can set some of it through COS's, but I want 1 COS to have 1 store server and another to use 2 store servers. I want Zimbra to automatically choose which server to put the users on in the second COS, but I want it evenly distributed. When I tested @5 users, they all went to 1 server. Any ideas on how it actually works? Should I just pick and choose which users go on each server?

Thanks!